TLS_BUFFER_get_offset
i = BIO_write(rl->bio, (char *)&(TLS_BUFFER_get_buf(thiswb)[TLS_BUFFER_get_offset(thiswb)]),
TLS_BUFFER_get_buf(thiswb) + TLS_BUFFER_get_offset(thiswb),
p += TLS_BUFFER_get_offset(rbuf);